These teachings relate generally to wireless telecommunication systems, including both fixed network and mobile user devices, and to an emerging function known generally as the Multimedia Broadcast/Multicast Service (MBMS).
The following abbreviations are herewith defined.
Reference can also be made to 3GPP TR21.905, V4.4.0 (2001-10), Third Generation Partnership Project; Technical Specification Group Services and System Aspects; Vocabulary for 3GPP Specifications (Release 4).
Referring to FIG. 1 by way of introduction, in conventional TDMA systems one frame is divided into time slots (TSs). In the case of GSM/GPRS there are eight time slots per frame (TS1-TS8). FIG. 2 illustrates the manner in which a physical channel (i.e., one RF channel operating at a defined carrier frequency) constitutes a series of time slots in consecutive TDMA frames. A plurality of TDMA frames, such as four, constitutes one block.
In (E)GPRS data is transferred in blocks (also referred to as radio blocks) each containing four block-interleaved bursts (one burst per time slot per frame). These blocks can carry varying amounts of information depending on the modulation and coding scheme that is used. Information from several logical channels, e.g., PDCH, PCCCH, PACCH, and so forth can be multiplexed into one physical channel. In other words one block can contain a PDCH block, the next PCCCH block and so on. It is also possible to multiplex several different users into one PDCH.
It is known in the art to provide for so-called multislot operation. More particularly, in order to support a specific data rate for some defined service the wireless network can allocate two or more physical channels (time slots) in parallel and allocate all or part of the radio blocks of the physical channel for the service. In this way the network can provide the required bit rates in a flexible manner.
MBMS is an emerging new service that is intended to provide enhanced functionality for advanced wireless communication systems, in particular the 3GPP(trademark) and similar types of networks. With MBMS it will be possible for MSs to receive both text and video data (e.g., video broadcasting).
However, a problem has arisen in that when allocated to a given physical channel for MBMS operation the MS can consume power in a substantially continuous manner, thereby shortening battery life and reducing the time between required rechargings of the battery. Furthermore, the MS is typically required to periodically perform certain non-communication related functions, such as making channel measurements from neighboring cells. In order to still perform these required functions it may be necessary to temporarily interrupt the reception of data from the MBMS service, which could be objectionable to the user.
FIG. 3 shows a case where all blocks in one physical channel (e.g., assuming the use of TS1) would be allocated for receiving the MBMS service at the MS. As is shown, the MS can be receiving MBMS services for relatively long periods of time, and such continuous reception of radio blocks consumes significantly more battery power than would be consumed if periodic reception were used. In the illustrated case the use of the MS low power consumption mode is not possible in the short time period between received bursts of consecutive TDMA frames within each radio block, it being remembered from above that each radio block contains four block-interleaved bursts (one burst per time slot per frame).
The foregoing and other problems are overcome, and other advantages are realized, in accordance with the presently preferred embodiments of these teachings.
The teachings in accordance with this invention provide an optimal or near optimal use of multislot channel allocation for MBMS in GERAN and other wireless networks that use time slotted radio communication channels.
A method is provided for allocating blocks for a MBMS channel based on the MS multislot class and on a required MBMS service bit rate. In accordance with this invention multislot transmission is used so as to both satisfy the required bit rate of the MBMS service and to reduce or minimize the MS power consumption. By allocating several time slots in parallel to one block, and by providing an idle period between allocated blocks, the MS is enabled to switch to a lower power consumption mode (e.g., enter the sleep mode), or alternatively the MS is enabled to perform system information decoding or neighbor cell monitoring) functions. This method overcomes the power consumption and other problems that result from an allocation of one channel continuously for MBMS service reception purposes.
The method allows the network to minimize the mobile station""s battery consumption by utilizing multislot reception. This is beneficial, as the MS can be receiving MBMS services for relatively long periods of time, and the continuous reception of radio blocks consumes significantly more battery power as compared to periodic reception. When the periodic reception mode is used the MS can transition to the lower power consumption mode for those times when the MBMS messages (or normal paging blocks) are not scheduled to be received by the MS.
A method of this invention is directed to operating a wireless telecommunication system for providing a MBMS broadcast transmission from a network operator to a mobile station. A first step determines a minimum bit rate requirement to broadcast a MBMS message and a number of radio blocks per time period that are required to satisfy the bit rate requirement. A second step allocates the determined number of radio blocks in accordance with a multislot transmission technique, wherein a plurality of time slots are used per frame, such that the mobile station is provided with at least one idle radio block between two active transmission periods, and may be provided with at least one idle radio block between two active (MBMS) radio blocks. A third step transmits the determined radio block allocation to the mobile station. In the preferred embodiment the step of determining may include a consideration of radio channel conditions and a multislot class of the mobile station.
In one embodiment the step of allocating attempts to maximize the number of idle radio blocks and the mobile station, in response to an occurrence of the at least one idle radio block, performs at least one of entering a reduced power consumption mode of operation during the at least one idle radio block or entering a neighbor cell measurement mode of operation during the at least one idle radio block, while in another embodiment the step of allocating allocates radio blocks so as to complete the data transmission within the shortest period of time.